Low-Cost Receiver Using Tracking Filter

ABSTRACT

A receiver ( 400 ) includes a tracking bandpass filter ( 420 ) and a signal processing circuit ( 430 - 480 ). The tracking bandpass filter ( 420 ) has a first input for receiving a radio frequency (RF) signal, and an output, and includes a first portion ( 731 ) on a semiconductor die ( 730 ), and at least one inductor ( 721 ). The at least one inductor ( 721 ) is operatively coupled to the first portion of the tracking bandpass filter ( 420 ). The signal processing circuit ( 430 - 480 ) has an input coupled to the output of the tracking bandpass filter ( 420 ), and an output for providing a processed signal. The semiconductor die ( 730 ) and the at least one inductor ( 721 ) are integrated into a single multi-chip module (MCM) ( 710 ).

CROSS REFERENCE TO RELATED, COPENDING APPLICATION

Related subject matter is found in a copending patent applicationentitled “Low-Cost Receiver Using Tracking Bandpass Filter and LowpassFilter,” application number unknown, attorney docket no. 1052-0046,invented by Ramin K. Poorfard, filed of even date herewith and assignedto the assignee hereof.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a radio frequency (RF)receiver and, more particularly relates to an RF receiver using atracking filter.

BACKGROUND

Radio frequency (RF) receivers are used in a wide variety ofapplications such as television receivers, cellular telephones, pagers,global positioning system (GPS) receivers, cable modems, cordlessphones, satellite radio receivers, and the like. As used herein, a“radio frequency” signal means an electrical signal conveying usefulinformation and having a frequency from about 3 kilohertz (kHz) tothousands of gigahertz (GHz), regardless of the medium through whichsuch signal is conveyed. Thus an RF signal may be transmitted throughair, free space, coaxial cable, fiber optic cable, etc. One common typeof RF receiver is the so-called superheterodyne receiver. Asuperheterodyne receiver mixes the desired data-carrying signal with theoutput of tunable oscillator to produce an output at a fixedintermediate frequency (IF). The fixed IF signal can then beconveniently filtered and converted back down to baseband for furtherprocessing. Thus a superheterodyne receiver requires two mixing steps.

For example, a television receiver may translate one channel in the bandof 48 megahertz (MHz) to 870 MHz to an intermediate frequency of 44 MHz.And within the United States, FM radios will typically translate FMaudio signals, which are broadcast in 200 KHz channels in the frequencyband from 88.1 MHz to 107.9 MHz, to an intermediate frequency of 10.7MHz. Because of the wide frequency range required of televisionreceivers, it has been difficult to design high quality televisionreceivers at low cost.

High quality television receivers have been traditionally formed withdiscrete components such as inductors, varactors, and capacitors. Whilethe performance of these receivers has been good, they are expensive andbulky. It would be desirable to utilize the cost advantage of modernintegrated circuit technologies. Unfortunately, existing silicon-basedtelevision tuners do not perform as well as discrete tuners and have notbecome significant in the marketplace. Moreover, television receiversthat do use integrated circuit technology while retaining acceptableperformance have still required external, discrete components, adding totheir cost. Thus the promise of integrated circuit technology inreducing the cost of television receivers has not been fully realized.

What is needed, then, are new receiver architectures for applicationssuch as television receivers that retain the high performance ofdiscrete receivers but also take advantage of the reduction in costafforded by integrated circuit technology.

SUMMARY

According to one embodiment, a receiver includes a tracking bandpassfilter and a signal processing circuit. The tracking bandpass filter hasa first input for receiving a radio frequency (RF) input signal, and anoutput. The tracking bandpass filter includes a first portion disposedon a semiconductor die, and at least one inductor. The at least oneinductor is operatively coupled to the first portion of the trackingbandpass filter. The signal processing circuit has an input coupled tothe output of the tracking bandpass filter, and an output for providinga processed signal. The semiconductor die and the at least one inductorare integrated into a single multi-chip module (MCM).

According to another embodiment, a receiver includes a tracking bandpassfilter, a power detector, a signal processing circuit, and amicrocontroller. The tracking bandpass filter has a first input forreceiving a radio frequency (RF) input signal, a second input forreceiving a center frequency adjustment signal, and an output. Thetracking bandpass filter includes a first portion disposed on asemiconductor die, and at least one inductor disposed on an integratedpassive device (IPD). The at least one inductor is operatively coupledto the first portion of the tracking bandpass filter. The power detectorincludes an input coupled to the output of the tracking bandpass filter,and an output. The signal processing circuit includes an input coupledto the output of the tracking bandpass filter, and an output forproviding a processed signal. The microcontroller includes an inputcoupled to the output of the power detector, and an output coupled tothe second input of the tracking bandpass filter for adjusting a centerfrequency of the tracking bandpass filter. The semiconductor die and theIPD die are integrated into a single multi-chip module (MCM).

According to yet another embodiment, a receiver includes a low noiseamplifier, a tracking bandpass filter, a local oscillator, a mixer, asignal processing circuit and a microcontroller. The low noise amplifierincludes a first input for receiving a radio frequency (RF) inputsignal, a second input for receiving a gain adjustment signal, and anoutput. The tracking bandpass filter includes a first input coupled tothe output of the low noise amplifier, a second input for receiving acenter frequency adjustment signal, and an output. The tracking bandpassfilter includes a first portion disposed on a semiconductor die, and atleast one inductor disposed on an integrated passive device (IPD). Theat least one inductor is operatively coupled to the first portion of thetracking bandpass filter. The local oscillator includes an input forreceiving a local oscillator frequency adjustment signal, and an outputfor providing a local oscillator signal at a frequency chosen to mix theoutput of the tracking bandpass filter to a desired intermediatefrequency (IF). The mixer includes a first input coupled to the outputof the tracking bandpass filter, a second input coupled to the output ofthe local oscillator, and an output for providing an IF signal at thedesired intermediate frequency. The signal processing circuit includesan input coupled to the output of the mixer, and an output for providinga processed signal. The microcontroller includes a first output coupledto the second input of the low noise amplifier for adjusting the gain ofthe low noise amplifier, a second output coupled to the second input ofthe bandpass filter for adjusting the center frequency of the bandpassfilter, and a third output coupled to the input of the local oscillatorfor adjusting the local oscillator frequency of the local oscillator.The semiconductor die and the IPD die are integrated into a singlemulti-chip module (MCM).

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings, in which:

FIG. 1 illustrates in partial block diagram and partial schematic form afirst television receiver known in the prior art;

FIG. 2 illustrates in partial block diagram and partial schematic form asecond television receiver known in the prior art;

FIG. 3 illustrates in partial block diagram and partial schematic form athird television receiver known in the prior art;

FIG. 4 illustrates in partial block diagram and partial schematic form atelevision receiver according to an embodiment of the present invention;

FIG. 5 illustrates in partial block diagram and partial schematic form aparticular embodiment of the television receiver of FIG. 4;

FIG. 6 illustrates in schematic form one of the tracking bandpassfilters of FIGS. 4 and 5;

FIG. 7 illustrates a top view of a multi-chip module (MCM) incorporatingthe receiver of FIG. 5; and

FIG. 8 illustrates a graph of the variation in passband response of thefilter of FIG. 6 as capacitance is varied that is useful inunderstanding a calibration procedure therefor.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

In general, a receiver as described herein uses a tracking bandpassfilter for channel tuning. The tracking bandpass filter includes aninductor that is fabricated on an integrated passive device (IPD) die.The receiver combines the IPD die and a main integrated circuit die intoa single multi-chip module (MCM). Thus to the user the receiver appearsto be a single integrated circuit. However the IPD die is well suited tobuilding inductors without using the relatively more-expensive siliconmanufacturing process. Thus, high quality, low cost, and compact sizeare obtained simultaneously.

In order to understand the difficulty of known receiver designs tosimultaneously achieve both high quality filtering and low cost,reference is now made to FIG. 1, which illustrates in partial blockdiagram and partial schematic form a first television receiver 100 knownin the prior art. Receiver 100 includes one or more radio frequency (RF)sections 110, an intermediate frequency (IF) section 130, a demodulatorsection 140, a radio frequency (RF) phase-locked loop (PLL) 152, acrystal 153, a DC-to-DC pulse width modulation (PWM) generator 154, aloop filter 156, and a varactor voltage control circuit 158. RF section110 includes a tracking filter 112, a low-noise amplifier (LNA) 114, atracking filter 116, a mixer 118, a local oscillator 120, and a tankcircuit 122. IF section 130 includes an intermediate frequency (IF)filter 132, an IF gain stage 134, a surface acoustic wave (SAW) filter136, and a variable gain IF gain stage 138. Demodulator section 140includes a demodulator 142, a peak detector 144, and a delay automaticgain control (AGC) 146.

Tracking filter 112 has a first input for receiving a radio frequency(RF) input signal labeled “RF_(IN)”, a second input for receiving acenter frequency adjustment voltage labeled “F_(CENTER)”, and an output.LNA 114 has a first input connected to the output of tracking filter112, a second input for receiving a gain control signal labeled “LNAAGC”, and an output. Tracking filter 116 has a first input connected tothe output of LNA 114, a second input for receiving voltage F_(CENTER),and an output. Mixer 118 has a first input connected to the output oftracking filter 116, a second input, and an output. IF filter 132 has aninput connected to the output of mixer 118, and an output. IF gain stage134 has an input connected to the output of IF filter 132, and anoutput. SAW filter 136 has an input connected to the output of IF gainstage 134, and an output. Variable gain IF gain stage 138 has a firstinput connected to the output of SAW filter 136, a second input, and anoutput. Demodulator 142 has an input connected to the output of variablegain IF gain stage 138, and an output for providing a demodulated outputsignal labeled “TV_(OUT)”.

Peak detector 144 has an input connected to the output of variable gainIF gain stage 138, and an output. Delay AGC 146 has an input connectedto the output of peak detector 144, a first output for providing a gainadjustment signal labeled “IF AGC” connected to the second input ofvariable gain IF gain stage 138, and a second output for providingsignal LNA AGC connected to the second input of LNA 114.

RF PLL 152 has a first input, a second input connected to crystal 153, afirst output and a second output. Loop filter 156 has a first inputconnected to the first output of RF PLL 152, a second input connected tothe second output of RF PLL 152, and an output for providing voltageF_(CENTER) connected to the second input of tracking filter 112 and tothe second input of tracking filter 116. DC-DC PWM GENERATOR 154 has anoutput. Varactor voltage control circuit 158 has an input connected tothe output of DC-DC PWM GENERATOR 154, and an output connected to theoutput of loop filter 156. Tank circuit 122 has an input for receivingvoltage F_(CENTER) from the output of loop filter 156, and an output.Local oscillator 120 has an input connected to the output of tankcircuit 122, and an output connected to the second input of mixer 118and also connected to the input of RF PLL 152.

Receiver 100 exhibits a degree of integration wherein mixer 118, IF gainstage 134, variable gain IF gain stage 138, local oscillator 120, RF PLL152 and DC-DC PWM generator 154 are included in a single integrateddevice known as a MOPLL 170 (i.e., Mixer, Oscillator, PLL). Further,demodulator 142, peak detector 144, and delay AGC 146 are included in asingle integrated device known as a demodulator die 160. Receiver 100also includes several discrete elements, including tracking filter 112,LNA 114, tracking filter 116, IF filter 132, SAW filter 136, the circuitelements of the loop filter 156 and the varactor voltage control circuit158.

In operation, signal RF_(IN) is a broadband signal that includes energyfrom several television signals modulated onto carrier waves atdifferent frequencies. The different carrier waves constitute thetelevision channels from which television content can be received.Signal RF_(IN) can be received from an antenna, or from a cabletelevision connection. Tuning into a desired television channel involvespassing signal RF_(IN) through tracking filter 112 and tracking filter116 to reduce the energy from the television signals modulated ontocarrier waves outside of the desired television channel carrier wavefrequency band. Tracking filter 112 and tracking filter 116 includeinductors and capacitors configured to give the desired order ofbandpass L-C (i.e., inductor-capacitor) filter response. LNA 114 isincluded to amplify the tuned signal while introducing minimal noiseproducts. Mixer 118 mixes the tuned signal with the output from localoscillator 120 and produces sum and difference output frequencies:

f ₁ =f _(CW) +f _(LO)   [1]

and

f ₂ =f _(CW) −f _(LO)   [2]

where f_(CW) is the frequency of the desired carrier wave of the tunedsignal, and f_(LO) is the local oscillator frequency. Local oscillator120 has an output frequency that is set by tank circuit 122. Tankcircuit 122 is a resonant L-C circuit. The signal component f₁ is ahigher frequency signal that is filtered out by IF filter 132. IF filter132 is a lowpass L-C filter. The component f₂ is an intermediatefrequency IF signal that includes the desired channel at a selected IFthat is passed by IF filter 132. The IF signal is further conditioned byIF gain stage 134, SAW filter 136, and variable gain IF gain stage 138before being demodulated into signal TV_(OUT) by demodulator 160. Peakdetector 144 detects power levels at the input of demodulator 142, andprovides feedback input to delay AGC 146 which adjusts the gain at LNA114 and variable gain IF gain stage 138, so that the power level of thetuned RF signal is not too high or too low.

In order to have the ability to tune in more than one televisionchannel, receiver 100 includes a tuning mechanism that adjusts thecenter frequency of tracking filter 112 and tracking filter 116, and thefrequency of the output of local oscillator 120. Tracking filter 112,tracking filter 116, and tank circuit 122 include high quality inductorsthat are typically air wound, and are not easily tuned to change circuitperformance. On the other hand, the capacitors are implemented withvaractors, that is, reverse-biased diodes designed such that thecapacitance varies with the applied voltage. The varactors are thustunable by varying the applied reverse-bias voltage. The reverse-biasvoltage used to achieve the desired capacitance can be up to 30 volts(V) or higher. Loop filter 156 and varactor voltage control circuit 158serve to adjust the voltage applied to the varactors in tracking filter112, tracking filter 116, and tank circuit 122 to tune to the varioustelevision channels.

Receiver 100 includes features which are not easily adaptable to higherlevels of integration. In particular, tracking filter 112, trackingfilter 116, and tank circuit 122 include high quality inductors that aretypically hand tuned at the time of manufacture to ensure proper tuningperformance in operation. Additionally, the use of varactors requiresthe addition of the components associated with loop filter 156, and withvaractor voltage control circuit 158 and DC-DC PWM generator 154, whichtogether function as a DC-to-DC converter. Also, use of SAW filter 136increases both the cost and the physical size of receiver 100. Receiver100 also requires wide tuning ranges for tracking filter 112, trackingfilter 116, and local oscillator 120.

Another known receiver architecture is shown in FIG. 2, whichillustrates in partial block diagram and partial schematic form a secondtelevision receiver 200 known in the prior art. Receiver 200 is anup-down receiver and includes a buffer 212, an attenuator 214, avariable low-noise amplifier (VLNA) 216, an RF mixer 218, a SAW filter220, a variable gain IF amplifier 224, an IF mixer 226, a SAW filter228, a variable gain IF amplifier 230, a demodulator 232, powerdetectors 234 and 236, an automatic gain control (AGC) circuit 238,local oscillators 240 and 242, phase-locked loops (PLLs) 244 and 246, acrystal oscillator 248, and a crystal 250.

Buffer 212 has an input for receiving an RF input signal RF_(IN), and anoutput. Attenuator 214 has a first input connected to the output ofbuffer 212, a second input, and an output. VLNA 216 has a first inputconnected to the output of attenuator 214, a second input, and anoutput. RF mixer 218 has a first input connected to the output of VLNA216, a second input, and an output. SAW filter 220 has an inputconnected to the output of RF mixer 218, and an output. Variable gain IFamplifier 224 has a first input connected to the output of SAW filter220, a second input, and an output. IF mixer 226 has a first inputconnected to the output of variable gain IF amplifier 224, a secondinput, and an output. SAW filter 228 has an input connected to theoutput of IF mixer 226, and an output. Variable gain IF amplifier 230has a first input connected to the output of SAW filter, a second input,and an output. Demodulator 232 has an input connected to the output ofvariable gain IF amplifier 230, a first output for providing ademodulated output signal TV_(OUT), and a second output for providing anAGC signal IF AGC connected to the second input of the variable gain IFamplifier 230.

Power detector 234 has an input connected to the output of VLNA 216, andan output. Power detector 236 has an input connected to the output of IFmixer 226, and an output. AGC circuit 238 has a first input connected tothe output of power detector 234, a second input connected to the outputof power detector 236, a first output for providing an AGC signallabeled “AGC_(RF)” connected to the second input of attenuator 214 andalso connected to the second input of VLNA 216, and a second output forproviding an AGC signal labeled “AGC_(IF)” connected to the second inputof variable gain IF amplifier 224. Crystal oscillator 248 is connectedto crystal 250, and has a first output and a second output. PLL 244 hasan input connected to the first output of crystal oscillator 248, and anoutput. Local oscillator 240 has an input connected to the output of PLL244 and an output connected to the second input of RF mixer 218. PLL 246has an input connected to the second output of crystal oscillator 248,and an output. Local oscillator 242 has an input connected to the outputof PLL 246 and an output connected to the second input of IF mixer 226.Receiver 200 exhibits a degree of integration wherein buffer 212,attenuator 214, variable low-noise amplifier (VLNA) 216, RF mixer 218,variable gain IF amplifier 224, IF mixer 226, variable gain IF amplifier230, power detectors 234 and 236, AGC circuit 238, local oscillators 240and 242, phase-locked loops (PLLs) 244 and 246, and crystal oscillator248 are combined on a single integrated circuit die 260.

Here, rather than tuning tracking bandpass filters and tank circuits tofilter out all but the desired channel, receiver 200 mixes the broadbandRF_(IN) signal with a local oscillator signal chosen to mix the desiredchannel to a high IF which is the center frequency of a highly selectivebandpass filter (e.g., SAW filter 220). The high IF is above a desiredIF, so receiver 200 then mixes the filtered signal to the desired IF. Inoperation, signal RF_(IN) is adjusted to a level that will not overpowerIF mixer 218 by first passing through buffer 212, attenuator 214 andVLNA 216. The power level at the input to RF mixer 218 is detected bypower detector 234 and AGC circuit 238 provides a gain adjustment signalto attenuator 214 and VLNA 216 via signal AGC_(RF). Mixer 118 combinesthe gain adjusted signal with the output from local oscillator 240, toproduce sum and difference output frequencies:

f ₁ =f _(RF) +f _(LO)   [3]

and

f ₂ =f _(RF) −f _(LO)   [4]

where f_(RF) is the carrier frequency of a desired channel of signalRF_(IN) and f_(LO) is the local oscillator frequency. Local oscillator240 is driven by PLL 244, which is adjusted such that the desiredchannel's spectrum is mixed into the passband of SAW filter 220. Thesignals f₁ and f₂ include components that correspond to the unfilteredsignal RF_(IN), but the undesired channel components are filtered out bySAW filter 220. The center frequency of SAW filter 220 is typicallyaround 1 gigahertz (GHz). IF mixer 226 combines the output of SAW filter220 with the output from local oscillator 242, to produce the desired IFsignal, which passes through SAW filter 228 and variable gain amplifier230 before being demodulated by demodulator 232 into signal TV_(OUT).

Receiver 200, with the high selectivity of SAW filter 220 solves severalproblems with receiver 100, such as elimination of discrete high qualityinductors, varactors and the associated DC-DC converter, and reductionof the LO tuning range. However, receiver 200 has introduced anadditional discrete component, SAW filter 228, so the reduction inoverall size is minor. Furthermore, the addition of the mixer 226 andPLL 246 to implement the up-down architecture makes the integratedcircuit die 260 larger. Also, the absence of tracking filters increasesthe linearity requirements for VLNA 216 and IF mixer 226, and results ingreater power consumption.

FIG. 3 illustrates in partial block diagram and partial schematic form athird television receiver 300 known in the prior art. Receiver 300includes a LNA 312, an attenuator 314, a tracking filter 316, an RF AGCamplifier 318, an RF filter 320, an RF polyphase filter 322, a mixer324, an IF polyphase filter 326, an IF lowpass filter 328, an IF AGCamplifier 330, a power detector 332, a digital control circuit 334, aDC-DC converter 336, a crystal 340, a crystal oscillator 342, asynthesizer 344, a loop filter 346, an oscillator 348, a test signalgenerator 350, a synthesizer 352, a loop filter 354, an oscillator 356,and a local oscillator generator 358.

LNA 312 has a first input for receiving an RF input signal RF_(IN), asecond input, and an output. Attenuator 314 has an input connected tothe output of LNA 312, and an output. Tracking filter 316 has a firstinput connected to the output of attenuator 314, a second input, and anoutput. RF AGC amplifier 318 has a first input connected to the outputof tracking filter 316, a second input, and an output. RF filter 320 hasan input connected to the output of RF AGC amplifier 318, and an output.RF polyphase filter 322 has an input connected to the output of RFfilter 320, and an output. Mixer 324 has a first input connected to theoutput of RF filter 320, a second input, and an output. IF polyphasefilter 326 has an input connected to the output of mixer 324, and anoutput. IF lowpass filter 328 has an input connected to the output of IFpolyphase filter 326, and an output. IF AGC amplifier 330 has a firstinput connected to the output of IF lowpass filter 328, a second input,and an output. Demodulator 360 has an input connected to the output ofIF AGC amplifier 330, and an output for providing a demodulated outputsignal TV_(OUT).

Power detector 332 has an input connected to the output of IF lowpassfilter 328, and an output. Digital control circuit 334 has an inputconnected to the output of power detector 332, a first output connectedto the second input of LNA 312, the second input of RF AGC amplifier318, and the second input of IF AGC amplifier 330, and a second output.DC-DC converter 336 has an input connected to the second output ofdigital control circuit 334, and an output connected to the second inputof tracking filter 316.

Crystal 340 has first and second terminals. Crystal oscillator 342 has afirst input connected through a capacitor to the first terminal ofcrystal 340, a second input connected through a capacitor to the secondterminal of crystal 340, a first output, and a second output.Synthesizer 344 has a first input connected to the first output ofcrystal oscillator 342, a second input, and an output. Loop filter 346has an input connected to the output of synthesizer 344, and an output.Oscillator 348 has an input connected to the output of loop filter 346,a first output connected to the second input of synthesizer 344, and asecond output. Test signal generator 350 has an input connected to thesecond output of oscillator 348, and an output connected to the firstinput of tracking filter 316. Synthesizer 352 has a first inputconnected to the second output of crystal oscillator 342, a secondinput, and an output. Loop filter 354 has an input connected to theoutput of synthesizer 352, and an output. Oscillator 356 has an inputconnected to the output of loop filter 354, a first output connected tothe second input of synthesizer 354, and a second output. Localoscillator generator 358 has an input connected to the second output ofoscillator 356, and an output connected to the second input of mixer324.

In operation, receiver 300 functions similarly to receiver 100, tuninginto a desired television channel by passing signal RF_(IN) throughtracking filter 316 to attenuate the television channels outside of thedesired passband. As such, tracking filter 316 includes inductors andvaractors. Receiver 300 exhibits a further degree of integration overreceivers 100 and 200, wherein LNA 312, attenuator 314, tracking filter316, RF AGC amplifier 318, RF filter 320, RF polyphase filter 322, mixer324, IF polyphase filter 326, IF lowpass filter 328, IF AGC amplifier330, power detector 332, digital control circuit 334, DC-DC converter336, crystal oscillator 342, synthesizer 344, oscillator 348, testsignal generator 350, synthesizer 352, and oscillator 356 are combinedon a system-in-package (SIP) receiver 370. In this approach, theinductors and varactors are surface mount devices (SMDs) soldered onto alaminate substrate along with a tuner die. The varactor SMDs are of ahigh voltage type, necessitating DC-DC converter 336, which operates atvoltages up to 30 volts. Thus, in order to integrate DC-DC converter 336onto the tuner die, the tuner die is implemented in a high voltagebipolar junction transistor complementary metal-oxide-silicon (HVBiCMOS) process.

To tune tracking filter 316, an off-line calibration tone is injectedfrom test signal generator 350 into tracking filter 316, and the powerlevel is measured at power detector 332. Because power measurement isdone in the IF section, two tones are needed in order to tune trackingfilter: the calibration tone, and the LO tone. Thus, two separatesynthesizers are required to perform calibration. While receiver 300achieves greater integration and a smaller footprint than receivers 100and 200, the necessity of SMD inductors and varactors, and the expensiveHV BiCMOS process means the cost savings are minimal compared toreceivers 100 and 200. Additionally, the requirement to include DC-DCconverter 336 and synthesizer 352 prevents further reduction in diesize. Thus, further integration while maintaining high performance wouldbe desirable.

FIG. 4 illustrates in partial block diagram and partial schematic form atelevision receiver 400 according to an embodiment of the presentinvention. Receiver 400 includes generally a low noise amplifier (LNA)410, a tracking bandpass filter 420, a preconditioning circuit 430, amixing circuit 440, a first intermediate frequency (IF) processingcircuit 450, a second IF processing circuit 460, a firstanalog-to-digital converter (ADC) 458, a second ADC 468, a demodulator480, a microcontroller unit (MCU) 490, and a power detector 491. LNA 410has a first input for receiving an RF input signal RF_(IN), a secondinput for receiving a gain control signal LNA AGC, and an output.Tracking bandpass filter 420 has a first input connected to the outputof LNA 410, a second input for receiving a tuning signal labeled“F_(BP)”, and an output.

Preconditioning circuit 430 includes an attenuator 432 and a filter 434.Attenuator 432 has a first input connected to the output of trackingbandpass filter 420, a second input for receiving an attenuation controlsignal labeled “ATTEN AGC”, and an output. Filter 434 has a first inputconnected to the output of attenuator 432, a second input for receivinga cutoff frequency adjustment signal labeled “F_(LP)”, and an output.

Mixing circuit 440 includes a local oscillator 442, and a mixer 444.Local oscillator 442 has an input for receiving a local oscillatortuning signal labeled “F_(LO)”, and a first output for providing twomixing signals, including an in-phase mixing signal and a quadraturemixing signal, and a second output for providing a test signal labeled“TEST” connected to the first input of tracking bandpass filter 420.Mixer 444 has a first input connected to the output of filter 434, asecond input connected to the output of local oscillator 442, a firstoutput for providing an in-phase IF signal, and a second output forproviding a quadrature IF signal.

IF circuit 450 has an input connected to the first output of mixer 444,and an output. IF circuit 460 has an input connected to the secondoutput of mixer 444, and an output. ADC 458 has an input connected tothe output of IF circuit 450, and an output for providing a 3-bitdigital output signal. ADC 468 has an input connected to the output ofIF circuit 460, and an output for providing a 3-bit digital outputsignal. Demodulator 480 has inputs connected to the outputs of ADCs 458and 468, and an output for providing a demodulated output signalTV_(OUT).

MCU 490 has an input, and outputs for providing the LNA AGC, F_(BP),ATTEN AGC, F_(LP), and F_(LO) control signals. Power detector 491 has aninput connected to the output of filter 434, and an output connected tothe input of MCU 490. MCU 490 can control receiver 400 by providingcontrol signals LNA AGC, F_(BP), ATTEN AGC, F_(LP), and F_(LO) asdiscrete outputs, as shown in FIG. 4, or by communicating the controlsignals over a serial interface from which they are received and driven.

In operation, receiver 400 functions as a television receiver adapted toreceive and demodulate television channels. MCU 490 is adapted tocontrol the various elements in receiver 400 according to the channelselected by the user. Receiver 400 uses a dual-filter architecture forthe pre-mixing tuner. Signal RF_(IN) is received and amplified asnecessary in LNA 410 under the control of MCU 490 via signal LNA AGC.Receiver 400 is thus able to present a signal to the input of trackingbandpass filter 420 at a suitable level. Receiver 400 utilizes digitalautomatic gain control using power detector 491 and MCU 490.

Tracking bandpass filter 420 is a second-order LC filter that assists inproviding image rejection by filtering neighboring channels, asignificant part of whose energy could be reflected back into thepassband. As will be described later with reference to FIG. 6, trackingbandpass filter 420 is implemented as an inductor with an array ofswitched capacitors, the selection of which functions to tune the centerfrequency of the passband of tracking bandpass filter 420 under thecontrol of MCU 490 via signal F_(BP). In calibrating tracking bandpassfilter 420, a test signal is provided to the first input of trackingbandpass filter 420, and the power output of filter 434 is measured bypower detector 491. As will be further described later with reference toFIG. 7, tracking bandpass filter 420 is implemented in part on anintegrated circuit substrate containing the other elements of receiver400, and part on an integrated passive device (IPD) die.

Attenuator 432 functions as a separately controllable gain element underthe control of MCU 490 via signal ATTEN AGC such that MCU 490 canproperly divide the attenuation between different portions of the signalprocessing path. Filter 434 provides additional attenuation above thethird harmonic of the mixing signal under the control of MCU 490 viasignal F_(LP) to prevent unwanted energy from a neighboring channel frombeing mixed into the passband. This frequency is important because localoscillator 442 uses a digital mixing signal that is a square wave, whichhas significant energy at its third harmonic.

Mixer 444 is a quadrature mixer that mixes the filtered and attenuatedRF input signal with the signal from local oscillator 442 to mix aselected channel to a desired IF. In receiver 400, the desired IF isselectable in the range of 3 to 5 megahertz (MHz), and thus receiver 400is configurable as a low-IF architecture. Additionally, receiver 400 isalso configurable as a direct down conversion receiver using zero IF. Toachieve the desired IF, local oscillator 442 is tuned to a frequencythat mixes the selected channel to the desired IF, under the control ofMCU 490 via signal F_(LO). In other embodiments, receiver 400 may use ahigh-IF architecture. After reading this disclosure, it will beappreciated that receiver 400 is configurable to be compatible withvarious television standards around the world.

Each of IF circuits 450 and 460 perform further signal conditioning,including lowpass filtering to pass signals below a cutoff frequency ofbetween 7 and 9 MHz, and further gain stages under the control of MCU490. ADCs 458 and 468 convert their respective input signals to thedigital domain, such that demodulator 480 can demodulate them digitallyand provide signal TV_(OUT).

By using the tracking bandpass filter approach with an LC type filter,receiver 400 is able to obtain high quality filtering and lowsignal-to-noise ratio at low cost. The RF filtering is shared betweentracking bandpass filter 420 and lowpass filter 434, which eases thequality required of tracking bandpass filter 420. The array of switchedcapacitors of tracking bandpass filter 420 is efficiently fabricated ona receiver die that also includes LNA 410, preconditioning circuit 430,mixing circuit 440, first intermediate frequency (IF) processing circuit450, second IF processing circuit 460, first analog-to-digital converter(ADC) 458, second ADC 468, demodulator 480, microcontroller unit (MCU)490, and power detector 491. Moreover, the inductors of trackingbandpass filter 420 are efficiently fabricated on an integrated passivedevice (IPD) die, as will be more fully explained with respect to FIG. 7below. Thus, receiver 400 achieves high quality at low cost.

FIG. 5 illustrates in partial block diagram and partial schematic form aparticular embodiment of the television receiver 500 of FIG. 4. Receiver500 includes an input section 510, first through fifth RF sections 520,530, 540, 550, and 560, a mixer load/I/Q combiner 528, a first IFsection 570, a second IF section 575, a demodulator 580 similar todemodulator 480, and an MCU 590 similar to MCU 490. Input section 510includes a first LNA 512, one or more additional LNA, labeled generallyas LNA 514, and a switch matrix 518. Each RF section 520, 530, 540, 550,and 560 includes a tracing bandpass filter 521 similar to trackingbandpass filter 420, an attenuator 522 similar to attenuator 532, amixer 524 similar to mixer 444, a power detector 525 similar to powerdetector 491, and a local oscillator 526 similar to local oscillator442. Further, first RF section 520, and second RF section 530 include afilter 523 similar to filter 434. IF section 570 includes an IF circuit572 similar to IF circuit 450, and an ADC 574 similar to ADC 458. IFsection 575 includes an IF circuit 577 similar to IF circuit 460, and anADC 579 similar to ADC 468.

Input section 510 receives an RF input signal RF_(IN). LNAs 512 through514 each have an input for receiving signal RF_(IN), and an output.Switch matrix 518 has a first input connected to the output of LNA 512,one or more additional inputs connected to the output of LNA 514, and athird input for receiving a switch matrix control signal labeled “SMCONTROL”, a first through a fifth output, and an RF dump output labeled“RF_(DUMP)”. RF sections 520, 530, 540, 550, and 560 each have an inputfor receiving an RF input signal that is connected to an outputs ofswitch matrix 518, such that the first output is connected to RF section520, the second output is connected to RF section 530, the third outputis connected to RF section 540, the fourth output is connected to RFsection 550, and the fifth output is connected to RF section 560. RFsections 520, 530, 540, 550, and 560 also each have a first output forproviding an in-phase IF signal, and a second output for providing aquadrature IF signal.

In each of RF sections 520 and 530, tracking bandpass filter 521 has afirst input connected through switch matrix 518 and an LNA 512 through514 to signal RF_(IN), a second input for receiving a tuning signal (notshown in FIG. 5) similar to tuning signal F_(BP), and an output.Attenuator 522 has a first input connected to the output of trackingbandpass filter 521, a second input for receiving an attenuation controlsignal (not shown in FIG. 5) similar to attenuation control signal ATTENAGC, and an output. Filter 523 has a first input connected to the outputof attenuator 522, a second input for receiving a cutoff frequencyadjustment signal (not shown in FIG. 5) similar to cutoff frequencyadjustment signal F_(LP), and an output. Local oscillator 526 has aninput for receiving a local oscillator tuning signal (not shown in FIG.5) similar to local oscillator tuning signal F_(LO), a first output forproviding two mixing signals, including an in-phase mixing signal and aquadrature mixing signal, and a second output for providing a testsignal TEST connected to the first input of tracking bandpass filter521. Mixer 524 has a first input connected to the output of filter 523,a second input connected to the output of local oscillator 526, a firstoutput for providing an in-phase IF signal, and a second output forproviding a quadrature IF signal. Power detector 525 has an inputconnected to the output of filter 523, and an output. RF sections 540,550, and 560 include elements that are connected together similarly toRF sections 520 and 530, except that, with no filter 523, the output ofattenuator 522 is connected to the first input of mixer 524. In analternative embodiment, filter 434 does not include a second input, butrather, is a lowpass filter with a cutoff frequency that issubstantially equal to twice the frequency of the low end of thefrequency range tuned by receiver 400.

Mixer load/I/Q combiner 528 has a first input pair connected to thefirst and second output of RF section 520, a second input pair connectedto the first and second output of RF section 530, a third input pairconnected to the first and second output of RF section 540, a fourthinput pair connected to the first and second output of RF section 550, afifth input pair connected to the first and second output of RF section560, a sixth input for receiving a mixer load/I/Q combiner controlsignal labeled “MLC CONTROL”, a first output for providing an in-phaseIF signal, and a second output for providing a quadrature IF signal.

IF section 570 receives the in-phase IF signal output from mixerload/I/Q combiner 528, and provides an in-phase digital signal todemodulator 580. Thus, IF circuit 572 has an input for receiving thein-phase IF signal, and an output. ADC 574 has an input connected to theoutput of IF circuit 572, and an output for providing a digitized outputsignal. IF section 575 receives the quadrature IF signal output frommixer load/I/Q combiner 528, and provides a digital signal todemodulator 580. Thus, IF circuit 577 has an input for receiving thequadrature IF signal, and an output. ADC 579 has an input connected tothe output of IF circuit 577, and an output for providing a digitizedoutput signal. Demodulator 580 has a first input connected to the outputof ADC 574, a second input connected to the output of ADC 579, and anoutput for providing a demodulated output signal labeled “TV_(OUT)”.

MCU 590 has five inputs, each connected to the output of one powerdetector 525, five outputs for providing signals F_(BP), five outputsfor providing signals ATTEN AGC, two outputs for providing signalsF_(LP), five outputs for providing signals F_(LO), an output connectedto the fourth input of switch matrix 518 for providing signal SMCONTROL, and an output connected to the sixth input of mixer load/I/Qcombiner 528 for providing signal MLC CONTROL. MCU 590 can implementsignals F_(BP), ATTEN AGC, F_(LP), F_(LO), SM CONTROL, and MLC CONTROLas discrete outputs, or signals F_(BP), ATTEN AGC, F_(LP), F_(LO), SMCONTROL, and MLC CONTROL can be implemented by placing the appropriatesignal values into buffer devices (not illustrated) which provide theoutputs.

In operation, receiver 500 functions as a television receiver similar toreceiver 400, being adapted to receive and demodulate televisionchannels in the range of 48 MHz to 1 GHz. MCU 590 is adapted to controlthe various elements in receiver 500 according to the channel selectedby the user. However, here, receiver 500 uses the dual filterarchitecture in RF sections 520 and 530, while RF sections 540, 550, and560 use a single filter architecture for the pre-mixing tuner. It willbe understood after reading this disclosure that different RF sectionscan be designed to provide filtering over a different portion of the 48MHz to 1 GHz range, and that such design can be easier to achieve thanwith a single RF section. Here, RF sections 520, 530, 540, 550, and 560are each designed to provide filtering and attenuation for a selectedfrequency range of signal RF_(IN). For example, in the illustratedembodiment, a first RF section 520 provides filtering and attenuation inthe range of 48 to 120 MHz, a second RF section 530 provides filteringand attenuation in the range of 120 to 240 MHz, a third RF section 540provides filtering and attenuation in the range of 240 to 470 MHz, afourth RF section 550 provides filtering and attenuation in the range of470 to 685 MHz, and a fifth RF section 560 provides filtering andattenuation in the range of 685 MHz to 1 GHz.

LNAs 512 through 514 receive and amplify signal RF_(IN). Receiver 500implements a number of LNAs 512 through 514 that is proportional to thedesired gain resolution (i.e., proportional to the number of gain stepsdesired). Switch matrix 518 receives the amplified signal RF_(IN) fromLNAs 512 through 514, and connects each LNA 512 through 514 to eitherthe RF section 520, 530, 540, 550, or 560 that is designed to providefiltering and attenuation for the selected channel, or to the RF_(DUMP)output under the control of MCU 590 via signal SM CONTROL. By switchingmore or less LNAs 512 and 514, receiver 500 is able to present signalRF_(IN) to the input of the selected one of RF sections 520, 530, 540,550, or 560 at a suitable power level for the selected tracking bandpassfilter 521, and mixer 524. MCU 590 uses the inputs from the selected oneof power detectors 525 to determine the number of LNAs 512 and 514 toswitch to the input of the corresponding RF sections 520, 530, 540, 550,or 560, thus achieving digital automatic gain control in receiver 500.In another embodiment, not illustrated, one or more LNA is designed toprovide variable linear amplification over a different portion of the 48MHz to 1 GHz range. It will be understood after reading this disclosurethat designing such LNAs is easier to achieve than designing a singleLNA covering the entire gain and tuning range. Here switch matrix 518receives signals from the LNAs 512 and 514 that together provide thedesired amplification, and switches each of them to the RF section 520,530, 540, 550, or 550 that is designed to provide filtering andattenuation for the selected channel. Further, MCU 590 controls the gainby controlling the switching properties of the switch matrix 518.

Each tracking bandpass filter 521 is a second-order LC filter that isimplemented as an inductor with an array of switched capacitors, theselection of which functions to tune the center frequency of thepassband of tracking bandpass filters 521 under the control of MCU 590via signals F_(BP), and is further implemented in part on an integratedcircuit substrate containing the other elements of receiver 400, andpart on an integrated passive device (IPD) die. Attenuators 522 functionas separately controllable gain elements under the control of MCU 490via signals ATTEN AGC. Filters 523 provide additional attenuation abovethe third harmonic of the mixing signal under the control of MCU 490 viasignals F_(LP) to prevent unwanted energy from a neighboring channelfrom being mixed into the passband. Again, this frequency is importantbecause local oscillators 526 use a digital mixing signal that is asquare wave, which has significant energy at its third harmonic. Afterreading this disclosure, it will be appreciated that a lowpass filtermay not be necessary to filter third harmonics of the digital mixingsignal frequency for RF sections that handle the higher frequencychannels.

Mixers 524 are quadrature mixers that mix the filtered and attenuated RFinput signal with the signal from local oscillators 526 to achieve adesired IF signal. Again, the desired IF is 4 MHz, and thus receiver 500utilizes a low-IF architecture. To achieve the desired IF, localoscillators 526 are tuned to a frequency that mixes a selected channelto the low IF frequency of 4 MHz, under the control of MCU 490 viasignal F_(LO). In other embodiments, receiver 500 may use a high-IF or adirect down conversion architecture. Mixer load/I/Q combiner 528receives the in-phase and quadrature IF signals from the selected mixer524 and switches them to the in-phase IF section 570 and the quadratureIF section 575, respectively, under the control of MCU 590 via signalMLC CONTROL.

Each of IF circuits 572 and 577 perform further signal conditioning,including lowpass filtering to pass frequencies below a cutoff frequencyof 7 MHz, and further attenuation. MCU 590 further has outputs, notshown in FIG. 5, for adjusting the gain of the signal through IFcircuits 572 and 577. ADCs 574 and 579 convert their respective inputsignals to the digital domain, such that demodulator 580 can demodulatethem digitally and provide signal TV_(OUT).

As with receiver 400, receiver 500 is able to obtain high qualityfiltering and low signal-to-noise ratio while operating at low cost byusing the tracking bandpass filter approach with an LC type filter.Again, the array of switched capacitors of tracking bandpass filters 521are efficiently fabricated on a low cost CMOS receiver die that alsoincludes input section 510, RF sections 520, 530, 540, 550, and 560,mixer load/I/Q combiner 528, IF sections 570 and 575, demodulator 580,and MCU 590. Likewise, the inductors of tracking bandpass filters 521are efficiently fabricated on an integrated passive device (IPD) die.Thus, receiver 500 also achieves high quality at low cost.

However, unlike receiver 400 of FIG. 4, receiver 500 separates thereceiver RF section in to five separate RF sections 520, 530, 540, 550,and 550 to relax the linearity requirements of the gain elements andtracking filters. This approach leads to further reduction in receiverdie size and cost. In another embodiment (not illustrated), filters 523can be included in additional RF stages 540, 550 or 560 in order tofilter images from energy from outside of the 40 MHz to 1 GHz range(e.g., from cellular communications above 1 GHz).

FIG. 6 illustrates in schematic form an embodiment of a trackingbandpass filter 600 suitable for use as tracking bandpass filters 420and 521 of FIGS. 4 and 5, respectively, and incorporating an array ofswitched capacitors to achieve center frequency tuning. As illustrated,tracking bandpass filter 600 includes a voltage to current (V-to-I)converter 602, a capacitor 604, an inductor 606, capacitors 611 through626, and transistors 632, 634, 636, 638, 640, 642, 644, and 646. V-to-Iconvert 602 has a differential input for receiving an RF input signallabeled “RF_(IN)”, and a differential output for providing an RF outputsignal labeled “FILTERED RF_(OUT)”. Tracking bandpass filter 600 alsoincludes an input for receiving a transistor control signal labeled“F_(BP) CONTROL”, and an input for receiving a reference voltage labeled“V_(REF)”. Capacitor 604 is connected between the differential output ofV-to-I converter 602. Inductor 606 is also connected between thedifferential output of V-to-I converter 602, and has a center tap forreceiving reverence voltage V_(REF). Capacitors 611, 613, 615, 617, 619,621, 623, and 625 each include a first terminal connected to thepositive side of the differential output of V-to-I converter 602, and asecond terminal. Capacitors 612, 614, 616, 618, 620, 622, 624, and 626each include a first terminal connected to the negative side of thedifferential output of V-to-I converter 602, and a second terminal.Transistors 632, 634, 636, 638, 640, 642, 644, and 646 are field effecttransistors (FETS) that each include a first source/drain terminalconnected to the second terminals of capacitors 611, 613, 615, 617, 619,621, 623, and 625, a gate for receiving the respective one of signalF_(BP), and a second source/drain terminal connected to the secondterminals of capacitors 612, 614, 616, 618, 620, 622, 624, and 626.

In operation, tracking bandpass filter 600 tunes its center frequency byswitching on one or more of transistors 632, 634, 636, 638, 640, 642,644, and 646. Transistors 632, 634, 636, 638, 640, 642, 644, and 646 areswitched on or off based upon the state of the individual gate of eachtransistor 632, 634, 636, 638, 640, 642, 644, and 646. In oneembodiment, the capacitance of capacitors 612 through 626 can be equalto each other (e.g., 1 picofarad (pF)), and so the overall capacitanceis 1 pF when only one transistor is on, 2 pF when two transistors areon, and so on until, where all eight transistors are on, the overallcapacitance is 8 pF, and tracking bandpass filter 600 can tune to eightdifferent channels. In another embodiment, tracking bandpass filter 600can tune to more or less than eight different channels by adding orremoving additional capacitor/transistor elements. In yet anotherembodiment, the capacitors can be binarily weighted, such that thecapacitance of capacitors 613 and 614 can be twice the capacitance ofcapacitors 611 and 612, the capacitance of capacitors 615 and 616 can betwice the capacitance of capacitors 613 and 614, and so on through tocapacitors 625 and 626 (e.g., capacitors 611 and 612=1 pF, capacitors613 and 614=2 pF, capacitors 615 and 616=4 pF, capacitors 617 and 618=8pF, capacitors 619 and 620=16 pF, capacitors 621 and 622=32 pF,capacitors 623 and 624=64 pF, and capacitors 625 and 626=128 pF). Inthis way, switching on various combinations of transistors 632, 634,636, 638, 640, 642, 644, and 646 permits 256 different capacitancevalues for tracking bandpass filter 600. It will be understood afterreading this disclosure that the transistors 632, 634, 636, 638, 640,642, 644, and 646 can be implemented as P-channel field effecttransistors (pFETs), bipolar junction transistors, or other transistortypes, as dictated by the design and fabrication considerations of thereceiver incorporating the tracking bandpass filter 600.

Incorporating switched capacitors to tune the center frequency of thepassband permits tracking bandpass filter 600 to be more fullyintegrated into a receiver die. This is because the switched capacitorarray replaces the varactors of receiver 100 and receiver 300, andeliminates the need for a DC-DC converter. Additionally, the receiverdie fabrication technology can be chosen to optimize performance RFperformance. Since capacitors are more easily implemented thaninductors, using switched capacitors to change the center frequency oftracking bandpass filter 600 makes the architecture of receivers 400 and500 easy to implement in an integrated circuit.

FIG. 7 illustrates a top view of a multi-chip module (MCM) 700incorporating the receiver of FIG. 5, wherein the tracking bandpassfilters are implemented using both an IPD die and a receiver die. Theelements of MCM 700 are representative, and are not shown in theiractual sizes or proportions. MCM 700 includes a substrate 710, an IPDdie 720, and a receiver die 730. IPD die 720 and receiver die 730 aremounted to substrate 710. IPD die 720 includes inductors 721, 722, 723,724, and 725, and a bond pad 728 for receiving reference voltageV_(REF). Each inductor 721, 722, 723, 724, and 725 has a pair of bondpads, shown typically on inductor 721 as bond pads 727 and 729. Receiverdie 730 includes switched capacitor arrays 731, 732, 733, 734, and 735,and a bond pad 738 for supplying reference voltage V_(REF). Eachswitched capacitor array 731, 732, 733, 734, and 735 has a pair of bondpads, shown typically on switched capacitor array 731 as bond pads 737and 739. Each inductor 721, 722, 723, 724, and 725 is connected to aswitched capacitor array 731, 732, 733, 734, and 735, respectively, suchthat a first connection is made between the bond pad 727 and bond pad737, and a second connection is made between the bond pad 729 and bondpad 739. Switched capacitor arrays 731, 732, 733, 734, and 735 areconnected to the rest of the receiver circuitry 740 on the die level.The rest of the receiver circuitry 740 is also configured to receive anRF input signal RF_(IN), and to provide a television output signalTV_(OUT).

By integrating an input section with LNAs and a switch matrix, multipleRF sections with the switched capacitor array portions of trackingbandpass filters, attenuators, and lowpass filters, a mixer load/I/Qcombiner, IF sections, demodulator and MCU on a single receiver die 730,and the inductor portions of tracking bandpass filters on an IPD die,greater levels of integration, size and cost reduction are achieved.Moreover, complimentary metal-oxide-semiconductor (CMOS) manufacturingprocesses require many process steps for formation of transistors andinterconnects. The inductors are formed on a low cost IPD die sinceinductors do not need many of the CMOS processing steps. However, MCM700 appears to be a single integrated circuit to the user.

Note that in other embodiments, the inductors on IPD 720 could beimplemented in other ways within MCM 700. For example, inductors 721-725could be implemented as discrete inductors, as traces in the substrateof MCM 700, and in other ways.

FIG. 8 illustrates graphs of the variation in frequency response of thefilter of FIG. 6 as capacitance is varied and is useful in understandinga calibration procedure therefore. A graph 801 illustrates the trackingbandpass filter 600. The vertical axis represents attenuation in dB andthe horizontal axis represents the frequency f in MHz. The spectrum fora desired channel is created by providing a test tone from the localoscillator 442 or 526, and the resulting power output is measured by thepower detector 491 or 525. Note that the tracking bandpass filter passesmore RF energy at frequencies above the desired channel frequency thanbelow the desired frequency. It is desirable to balance the RF energypassed above the desired channel frequency with the energy passed belowthe desired frequency, or, in other words, to center the trackingbandpass filter.

To center the bandpass tracking filter, the MCU finds the peak powerlevel, and the low and high frequency roll-off by switching offcapacitors in the switched capacitor array, moving the attenuation curveto the left as illustrated in the graph 802, and switching on capacitorsin the switched capacitor array, moving the attenuation curve to theright as illustrated in the graph 803. As the MCU switches capacitorsoff and on, the power detector measures the output power of the trackingbandpass filter, and the MCU can thus determine which switch combinationresults in the peak power output, the low frequency roll-off point andthe high frequency roll-off point.

The low and high frequency roll-off points can be defined, for example,as the points where the power level is −3 dB below the peak power. In aparticular embodiment, the center of the attenuation curve is determinedby setting the capacitance of the tracking bandpass filter to be thecapacitance level that is half way between the capacitance level of thelow frequency roll-off point and the capacitance level of the highfrequency roll-off point, as illustrated in the graph 804. In anotherembodiment, the MCU can record the power level of each switchcombination, to determine if one side of the attenuation curve rolls offfaster than the other, and can apply an appropriate correction factor indetermining the center of the attenuation curve.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments that fall within thetrue scope of the claims. Thus, to the maximum extent allowed by law,the scope of the present invention is to be determined by the broadestpermissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdetailed description.

1. A receiver, comprising: a tracking bandpass filter having a firstinput for receiving a radio frequency (RF) input signal, and an output,wherein said tracking bandpass filter comprises: a first portiondisposed on a semiconductor die; and at least one inductor operativelycoupled to said first portion of said tracking bandpass filter, and asignal processing circuit having an input coupled to said output of saidtracking bandpass filter, and an output for providing a processedsignal, wherein said semiconductor die and said at least one inductorare integrated into a single multi-chip module (MCM).
 2. The receiver ofclaim 1, wherein said at least one inductor is disposed on an integratedpassive device (IPD) die.
 3. The receiver of claim 1, wherein saidtracking bandpass filter is characterized as being an L-C type bandpassfilter and wherein said first portion comprises a switched capacitorarray.
 4. The receiver of claim 3, wherein: said tracking bandpassfilter further has a second input for receiving a center frequencyadjustment signal; and the receiver further comprises a microcontrollerhaving an output operably coupled to said second input of said trackingbandpass filter for adjusting a center frequency of said trackingbandpass filter.
 5. The receiver of claim 4, wherein: saidmicrocontroller further has an input; and the receiver furthercomprising a power detector having an input coupled to said output ofsaid tracking bandpass filter, and an output coupled to said input ofsaid microcontroller.
 6. The receiver of claim 5, wherein saidmicrocontroller is adapted to adjust said center frequency of saidtracking bandpass filter based upon the power level at said output ofsaid tracking bandpass filter, as measured by said power detector. 7.The receiver of claim 6, wherein said microcontroller is adapted toadjust said center frequency of said tracking bandpass filter bycontrolling said switched capacitor array.
 8. The receiver of claim 1,wherein said tracking bandpass filter is characterized as being secondorder.
 9. A receiver comprising: a tracking bandpass filter having afirst input for receiving a radio frequency (RF) input signal, a secondinput for receiving a center frequency adjustment signal, and an output,wherein said tracking bandpass filter comprises: a first portiondisposed on a semiconductor die; and at least one inductor disposed onan integrated passive device (IPD) die, said at least one inductoroperatively coupled to said first portion of said tracking bandpassfilter a power detector having an input coupled to said output of saidtracking bandpass filter, and an output; a signal processing circuithaving an input coupled to said output of said tracking bandpass filter,and an output for providing a processed signal; and a microcontrollerhaving an input coupled to said output of said power detector, and anoutput coupled to said second input of said tracking bandpass filter foradjusting a center frequency of said tracking bandpass filter; andwherein said semiconductor die and said IPD die integrated into a singlemulti-chip module (MCM).
 10. The receiver of claim 9, wherein saidtracking bandpass filter is characterized as being an L-C type bandpassfilter.
 11. The receiver of claim 10, wherein said first portioncomprises a switched capacitor array.
 12. The receiver of claim 11,wherein said microcontroller is adapted to adjust said center frequencyof said tracking bandpass filter based upon the power level at saidoutput of said tracking bandpass filter, as measured by said powerdetector.
 13. The receiver of claim 12, wherein said microcontroller isadapted to adjust said center frequency of said tracking bandpass filterby controlling said switched capacitor array.
 14. The receiver of claim9, wherein said tracking bandpass filter is characterized as beingsecond order.
 15. A receiver, comprising: a low noise amplifier having afirst input for receiving a radio frequency (RF) input signal, a secondinput for receiving a gain adjustment signal, and an output; a trackingbandpass filter having a first input coupled to said output of said lownoise amplifier, a second input for receiving a center frequencyadjustment signal, and an output, wherein said tracking bandpass filtercomprises: a first portion disposed on a semiconductor die; and at leastone inductor disposed on an integrated passive device (IPD) die, said atleast one inductor operatively coupled to said first portion of saidtracking bandpass filter a local oscillator having an input forreceiving a local oscillator frequency adjustment signal, and a firstoutput for providing a first local oscillator signal at a frequencychosen to mix said output of said tracking bandpass filter to a desiredintermediate frequency (IF); a mixer having a first input coupled tosaid output of said tracking bandpass filter, a second input coupled tosaid first output of said local oscillator, and a first output forproviding a first IF signal at said desired intermediate frequency; asignal processing circuit having a first input coupled to said firstoutput of said mixer, and an output for providing a processed signal;and a microcontroller having: a first output coupled to said secondinput of said low noise amplifier for adjusting said gain of said lownoise amplifier; a second output coupled to said second input of saidbandpass filter for adjusting said center frequency of said bandpassfilter; and a third output coupled to said input of said localoscillator for adjusting said first local oscillator frequency of saidlocal oscillator; and wherein said semiconductor die and said IPD dieare integrated into a single package.
 16. The receiver of claim 15,wherein said semiconductor die further comprises said low noiseamplifier, said first portion of said tracking bandpass filter, saidlocal oscillator, said mixer, said signal processing circuit, and saidmicrocontroller.
 17. The receiver of claim 16, wherein said first localoscillator signal is characterized as being a square wave signal. 18.The receiver of claim 16, further comprising: a lowpass filter having afirst input coupled to said output of said bandpass filter, a secondinput for receiving a corner frequency adjustment signal, and an outputcoupled to said input of said mixer; and said microcontroller furtherhaving a fourth output coupled to said second input of said lowpassfilter for adjusting a corner frequency of said lowpass filter.
 19. Thereceiver of claim 18, wherein said semiconductor die further comprisessaid lowpass filter.
 20. The receiver of claim 16, wherein: said localoscillator further has a second output for providing a second localoscillator signal in quadrature with said first local oscillator signal;said mixer having a third input coupled to said second output of saidlocal oscillator, and a second output for providing a second IF signalat said desired intermediate frequency; and said signal processingcircuit having a second input coupled to said second output of saidmixer.